This invention pertains to improvements in apparatus for performing dental x-ray examinations. The invention features a better way to shield a dental x-ray tube head for preventing emanation of unwanted stray radiation.
Dental x-ray apparatus customarily has the x-ray tube enclosed in an oil filled housing called a tube head. The lower wall of the tube head has an opening through which the primary x-ray beam is projected from the x-ray tube target toward the examination subject. A tubular member, called a cone, is coupled to the tube head axially of the opening to assist in aiming the x-ray beam at the proper zone on the subject's face. Heretofore, the x-ray tube head or housing has been lined with an x-ray shield such as sheet lead to prevent the stray radiation, that is, radiation other than that in the primary beam, from emanating in all directions through the walls of the housing. Most of the sheet lead is usually disposed on the inside wall of the housing so that it encloses a volume which is substantially the same as the volume of the housing. One reason for arranging the lead sheet in this way is to avoid having it be too close to the x-ray tube and other components in the tube head which have high voltage applied to them.
The use of a large amount of lead for shielding results in a tube head that has undesirably great weight and size. A consequence is that the pantograph type of tube head support arm, which is usually used to support the tube head for movement with all degrees of freedom, must be designed for handling the unduly high weight. It is more difficult to support a heavy tube head in such manner that it will remain in equilibrium when positioned near the patient than it is to support a lighter tube head. Moreover, when pieces of lead sheet are used for shielding, there is a greater chance for radiation to leak through a joint.
A primary object of the present invention is to over-come the above noted disadvantages and other disadvantages by providing a new method and structure for shielding a dental x-ray tube head.
A more specific object of the invention is to obviate the use of sheet lead for shielding a dental x-ray tube head.
Yet another object is to provide an x-ray tube shield which serves the dual purposes of supporting the tube and shielding it against radiating in undesired directions.
Still another object is to provide a shield that extends through the housing between the shield that surrounds the x-ray tube and the x-ray head cone and which is arranged in such manner that the external cone can be made much shorter than in prior designs.
A more specific object is to provide shielding components in an x-ray tube head which are comprised of dielectric resin impregnated with barium sulphate which can be molded to form shielding components in the most advantageous configurations for reducing the volume that is required for shielding. An adjunct of this object is to obtain a tube head that has reduced size and weight.
In accordance with the invention, in a dental x-ray tube head comprising a housing having an x-ray tube mounted in it, there are improved shielding means for preventing stray radiation from emanating outside of the path of the primary x-ray beam, the shielding means including a hollow element encasing the x-ray tube and having an aperture through which the primary beam projects, said element being comprised of a mixture of resin and barium sulphate. A further improvement results from use of a conical element for defining the beam path from the x-ray tube to outside of the housing wherein the conical element has shielding liner comprised of resin impregnated with barium sulphate.
How the foregoing and other more specific objects of the invention are achieved will appear in the more detailed description of a preferred embodiment of the invention which will now be set forth in reference to the drawings.